Elucidating the role of the integrated Type VI Secretion / Type I Fimbrial System in bacterial host infection

• Applicant: Dr. Andreas Diepold
• Subject Area: Medical Microbiology and Mycology, Hygiene, Molecular Infection Biology ; Metabolism, Biochemistry and Genetics of Microorganisms
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564500309

To understand – and eventually interfere with – bacterial virulence, we need to appreciate how bacteria employ their virulence factors. All pathogenic Yersinia, but also other, mostly opportunistic, bacterial pathogens, encode a peculiar version of a type VI secretion system (T6SS), where a complete set of T6SS genes is interspersed with genes encoding components of type I fimbriae (T1F), extracellular appendages often used for attachment to biotic surfaces. Leveraging on the presence of a single T6SS/T1F cluster in Yersinia enterocolitica, this project aims to characterize the function and benefit of this combination of virulence factors, both in defined conditions and in models that replicate the intestinal microenvironment. In preliminary experiments, we have visualized the assembly and activity of the Y. enterocolitica T6SS, identified a transcriptional activator for the T6SS/T1F cluster and co-regulated proteins that may constitute secreted virulence proteins, and isolated a constitutively T6SS-positive mutant strain. We also have established undifferentiated and differentiated host infection models for the visualization of bacterial infection and competition. In this project, we will first identify the activation conditions of the T6SS/T1F gene cluster, verify the functionality of the T6SS and its associated fimbrial genes, define the T6SS secretome and its physiological function, and characterize the interplay between T6SS and T1F under defined conditions in Y. enterocolitica. This will reveal when and where the T6SS and T1F are employed and yield initial information on their effect and target cell type. In the second part, we will determine the physiological function and targets of the T6SS/T1F and elucidate the overall function of this conserved cluster in pathogenesis. We will test for anti-prokaryotic and anti-eukaryotic activity of the Y. enterocolitica T6SS/T1F in competition and infection models. Finally, we will use these findings to define the overall role of the conserved integrated T6SS/T1F systems in bacterial infection. Our investigation will provide new insights on the role of the T6SS, T1F and their interaction in the pathogenesis of Y. enterocolitica, and elucidate the benefit of the widespread joint occurrence of these two systems in pathogenic bacteria.

• DFG Programme: Research Grants